A shoe sole is generally required to be light-weight, durable, gripping, shock-absorbing, bendable, etc., and each of these properties needs to be on a certain level or better while some of them are in a tradeoff relationship. In recent years, there has been a demand for better designing the tread surface of a shoe sole and for taking environmental considerations with a shoe sole.
With court shoes, cross-training shoes, etc., for example, the outsole often covers the entire surface of the midsole in view of the durability and the gripping property. However, an outsole, which is made of a non-foamed rubber material or a rubber material with a small expansion ratio, covering the entire surface of the midsole leads to an increase in the weight of the shoe sole. Conversely, if the midsole is partially exposed for a reduced weight, such exposed portions will generate weaknesses in view of durability.